Change in Emiliania huxleyi Virus Assemblage Diversity but Not in Host Genetic Composition during an Ocean Acidification Mesocosm Experiment

Abstract

Effects of elevated pCO2 on Emiliania huxleyi genetic diversity and the viruses that infect E. huxleyi (EhVs) have been investigated in large volume enclosures in a Norwegian fjord. Triplicate enclosures were bubbled with air enriched with CO2 to 760 ppmv whilst the other three enclosures were bubbled with air at ambient pCO2; phytoplankton growth was initiated by the addition of nitrate and phosphate. E. huxleyi was the dominant coccolithophore in all enclosures, but no difference in genetic diversity, based on DGGE analysis using primers specific to the calcium binding protein gene (gpa) were detected in any of the treatments. Chlorophyll concentrations and primary production were lower in the three elevated pCO2 treatments than in the ambient treatments. However, although coccolithophores numbers were reduced in two of the high-pCO2 treatments; in the third, there was no suppression of coccolithophores numbers, which were very similar to the three ambient treatments. In contrast, there was considerable variation in genetic diversity in the EhVs, as determined by analysis of the major capsid protein (mcp) gene. EhV diversity was much lower in the high-pCO2 treatment enclosure that did not show inhibition of E. huxleyi growth. Since virus infection is generally implicated as a major factor in terminating phytoplankton blooms, it is suggested that no study of the effect of ocean acidification in phytoplankton can be complete if it does not include an assessment of viruses.

Scientists’ warning to humanity: microorganisms and climate change

“…Responses to CO 2 levels differ between communities (for example, between Arctic phytoplankton and Antarctic phytoplankton 110 ). A mesocosm study identified variable changes in the diversity of viruses that infect E. huxleyi when it is growing under elevated volume 17 | SePTemBeR 2019 | 573 NATuRe RevIeWS | MiCrobiology CO 2 levels, and noted the need to determine whether elevated CO 2 levels directly affected viruses, hosts or the interactions between them 111 . These examples illustrate the need to improve our understanding of evolutionary processes and incorporate that knowledge into predictions of the effects of climate change.…”

Impact of dust addition on the microbial food web under present and future conditions of pH and temperature

“…Expected increased temperature and acidification might have complex effects on the microbial loop by modifying microbial and viral and community (e.g., Highfield et al, 2017;Krause et al, 2012;Hu et al, 2021;Allen et al, 2020;Malits et al, 2021). While increasing temperature in combination with nutrient input might enhance heterotrophic bacterial growth (Degerman et al, 2012;Morán et al, 2020) more than PP (Marañón et al, 2018), future environmental conditions could push even further this microbial community towards heterotrophy.…”

Why Are Algal Viruses Not Always Successful?

“…High CO 2 concentrations and the associated low pH have been linked to higher viral decay in aquatic systems. Larsen et al [ 109 ] as well as Highfield et al [ 110 ] found that abundances of EhV particles and a group of unidentified dsDNA viruses that infect nanoeukaryotes decreased with increasing CO 2 concentrations. Burst sizes have also been shown to be negatively affected in EhVs and PgVs, being reduced from 2890 to 2032 viruses per host cell [ 109 ] and by almost 14% [ 111 ], respectively.…”